ON SEPT. 21,2001, 10 days after two hijacked planes turned the twin towers of the World Trade Center into effigies of ash and killed 2,753 people, Mike Piazza hit a home run for the New York Mets.

It was the 312th of a career in which he hit 427. He had hit one two days earlier, in Pittsburgh, and he would hit another four nights later, in Montreal. But this was Piazza's first home game in the aftermath of what would become known simply as 9/11, in front of 41,235 people who had come to Shea Stadium still throbbing with grief and shock and uncertainty and fear. He came up in the eighth against Steve Karsay of the Atlanta Braves and was behind in the count 0-and-1. The Mets were behind by a run, with a runner at first. Piazza swung at a 94 mph fastball intended for the outside of the plate, and Karsay did not have to turn around to find out where it went. If he couldn't tell by the sound of the bat, he could tell by the roar of the crowd, the choir of throats unthrottled by a sense of relief and even deliverance.

It was a hit that scored two runs and won the game for the Mets 3-2. But it was of course much more than that, because Piazza did not hit his home run in the context of baseball but rather in the context of history-of mass murder perpetrated for global consumption and ultimately of unceasing war. He had done all a baseball player could do and hit his pitch; he had done all a human being could do and risen to his moment. He had answered, and such is the nature of sports-such is the nature of our relationship with sports-that in the 23 seconds required for him to round the bases, we claimed his answer as our own.

We love sports because they're beautiful, because they keep us in touch with the inexplicable and the extraordinary, and because we watch them through a lens unavailable to any other form of entertainment, one that obscures the divide between spectator and participant. We do not ask athletes only to play for us; we ask them to represent us, first where we are from and finally who we are. It is a form of faith, the belief that in what they do there is something of us, and so we cannot help but place their accomplishments at the far end of human capability.

We amplify, we exaggerate, we resort to metaphors that confer upon athletic achievements a cosmic dimension, so that when we see a play that strains credulity, we say we have witnessed a miracle, and when we praise athletes whose fame rests on their ability to rise routinely to the fleeting occasion, we insist that they are immortals. We have developed a moral language to describe what sports mean to us, and so it is inevitable both that we habitually speak of a hard-fought contest as nothing less than a war and that when real war comes to us, we turn to our athletes to deliver nothing less than a heroic response.

War came to us on Sept. 11, 2001, in the guise of catastrophe, and over the past 17 years, neither war nor catastrophe has ever left. We've not had the luxury to stop looking for heroes, and heroes have never had the luxury to stop being heroic.

The Mets wore embroidered patches commemorating those lost in the 9/11 attacks when they took the field on Sept. 21, 2011. Getty Images

It is an astonishment of our time how often we have asked athletes to help ease our sense of helplessness in the face of disaster, and how faithfully they've answered the call, on the field and off. They have showed up after storms, after floods, after bombings, after shootings, after attacks on sport itself; they have won Super Bowls and World Series in the name of drowned cities, they have showed their strength when challenged to be #Strong, they have used their fervor to spearhead fundraising, they have comforted the displaced, they have become part of the national relief effort for a nation so often under duress.

Yet something has changed since Piazza hit his 312th home run, for the precise reason that nothing has changed. Seventeen years ago, it was still possible to think of catastrophe in terms of sports-to believe that we'd be able to rally, turn the tide and emerge victorious as long as we played together as a team. Today, the United States of America is such a painfully divided nation that sports themselves are cited as part of the division.

Today, we have to think of sports in terms of catastrophe so that we can learn from catastrophe what is important, what will endure and what, in the end, will unify.

The thing that distinguishes catastrophe from tragedy is scale-the public rather than the personal nature of the event, the sheer range of tragedy that can be encompassed under a single heading. Sept. 11, 2001, became 9/11 because the attacks on our country tapped into vast energies at once physical and historical, and because the acts of terror were, in fact, terrifying, to the extent that we have never quite shaken the shadow of vulnerability they introduced to our national life. It was almost unfair to ask anyone, much less a baseball player, to come up with a reply to the heaped ruin still smoking and burning in lower Manhattan, but reply Piazza did, the only way he knew how, extending his arms and lining the ball over the left-center-field wall.

It traveled just over 420 feet, a distance that, if he had hit the ball up rather than out, would have made it not quite a third of the way up the towers that now stood only among the ghosts of memory. It was a speck, an ephemera-and yet, if it was dwarfed by the scale of all that was lost, still it was not diminished.

Piazza's jersey is now on display in the National September 11 Memorial & Museum. Jin Lee

Did the blow that Piazza struck also strike a blow against terror, as some had it? Did it send a message? Did it function as a statement of national resolve? It did none of those things and wasn't meant to. It was remarkable, yes ... remarkable in that it returned us to the routine. It changed nothing, but it added something, a proviso that disaster is not all that occurs in the blink of an eye, that belief is sometimes rewarded, that the fates do not fly on a fixed course, that a preponderance of the bad does not preclude the emergence of the good, as sudden and instantaneous as the crack of a bat.

These might be small things. But they are small, good things, sport's true purview, and on the night of Sept. 21, 2001, they turned out to be necessary to the families who had come to Shea Stadium mourning losses that were permanent, that were forever, that could not be reversed on a single mighty swing on an 0-1 count, but who found in a single mighty swing a reason to smile, an evanescent mercy they understood to be, for a few minutes anyway, mercy enough.

Piazza's home run was not the only time baseball offered the grace of an indelible moment in the wake of 9/11. There were other dramatic homers and other game-winning hits; there was also the pitch President George W. Bush threw in the 2001 World Series, the strike he tossed when the New York Yankees came back home down 2-0 to the Arizona Diamondbacks. But that was a different sort of gesture from Piazza's historically resonant hit, in part because Bush practiced and prepared for it and in part because it was intended as a gesture, a demonstration of determination on the part of a commander in chief about to take his country to war. That war has not yet ended, but that pitch now seems like a long time ago, as catastrophe keeps requiring that athletes contribute to their communities in the largest and smallest of possible ways, and keeps reminding us why sports occupy such a central place in our lives:

Because they are not war. Because we cheer for them and root for them and sweat for them and sometimes grieve for them as a higher form of peace.